OK, let's work through this together. We're starting with 21 and we're going to multiply it by 380, which means we add 21 to itself 380 times.
Step 1: 0 + 21 = 21
Step 2: 21 + 21 = 42
Step 3: 42 + 21 = 63
Step 4: 63 + 21 = 84
Step 5: 84 + 21 = 105
Step 6: 105 + 21 = 126
Step 7: 126 + 21 = 147
Step 8: 147 + 21 = 168
Step 9: 168 + 21 = 189
Step 10: 189 + 21 = 210
Step 11: 210 + 21 = 231
Step 12: 231 + 21 = 252
Step 13: 252 + 21 = 273
Step 14: 273 + 21 = 294
Step 15: 294 + 21 = 315
Step 16: 315 + 21 = 336
Step 17: 336 + 21 = 357
Step 18: 357 + 21 = 378
Step 19: 378 + 21 = 399
Step 20: 399 + 21 = 420
Step 21: 420 + 21 = 441
Step 22: 441 + 21 = 462
Step 23: 462 + 21 = 483
Step 24: 483 + 21 = 504
Step 25: 504 + 21 = 525
Step 26: 525 + 21 = 546
Step 27: 546 + 21 = 567
Step 28: 567 + 21 = 588
Step 29: 588 + 21 = 609
Step 30: 609 + 21 = 630
Step 31: 630 + 21 = 651
Step 32: 651 + 21 = 672
Step 33: 672 + 21 = 693
Step 34: 693 + 21 = 714
Step 35: 714 + 21 = 735
Step 36: 735 + 21 = 756
Step 37: 756 + 21 = 777
Step 38: 777 + 21 = 798
Step 39: 798 + 21 = 819
Step 40: 819 + 21 = 840
Step 41: 840 + 21 = 861
Step 42: 861 + 21 = 882
Step 43: 882 + 21 = 903
Step 44: 903 + 21 = 924
Step 45: 924 + 21 = 945
Step 46: 945 + 21 = 966
Step 47: 966 + 21 = 987
Step 48: 987 + 21 = 1008
Step 49: 1008 + 21 = 1029
Step 50: 1029 + 21 = 1050
Step 51: 1050 + 21 = 1071
Step 52: 1071 + 21 = 1092
Step 53: 1092 + 21 = 1113
Step 54: 1113 + 21 = 1134
Step 55: 1134 + 21 = 1155
Step 56: 1155 + 21 = 1176
Step 57: 1176 + 21 = 1197
Step 58: 1197 + 21 = 1218
Step 59: 1218 + 21 = 1239
Step 60: 1239 + 21 = 1260
Step 61: 1260 + 21 = 1281
Step 62: 1281 + 21 = 1302
Step 63: 1302 + 21 = 1323
Step 64: 1323 + 21 = 1344
Step 65: 1344 + 21 = 1365
Step 66: 1365 + 21 = 1386
Step 67: 1386 + 21 = 1407
Step 68: 1407 + 21 = 1428
Step 69: 1428 + 21 = 1449
Step 70: 1449 + 21 = 1470
Step 71: 1470 + 21 = 1491
Step 72: 1491 + 21 = 1512
Step 73: 1512 + 21 = 1533
Step 74: 1533 + 21 = 1554
Step 75: 1554 + 21 = 1575
Step 76: 1575 + 21 = 1596
Step 77: 1596 + 21 = 1617
Step 78: 1617 + 21 = 1638
Step 79: 1638 + 21 = 1659
Step 80: 1659 + 21 = 1680
Step 81: 1680 + 21 = 1701
Step 82: 1701 + 21 = 1722
Step 83: 1722 + 21 = 1743
Step 84: 1743 + 21 = 1764
Step 85: 1764 + 21 = 1785
Step 86: 1785 + 21 = 1806
Step 87: 1806 + 21 = 1827
Step 88: 1827 + 21 = 1848
Step 89: 1848 + 21 = 1869
Step 90: 1869 + 21 = 1890
Step 91: 1890 + 21 = 1911
Step 92: 1911 + 21 = 1932
Step 93: 1932 + 21 = 1953
Step 94: 1953 + 21 = 1974
Step 95: 1974 + 21 = 1995
Step 96: 1995 + 21 = 2016
Step 97: 2016 + 21 = 2037
Step 98: 2037 + 21 = 2058
Step 99: 2058 + 21 = 2079
Step 100: 2079 + 21 = 2100
Step 101: 2100 + 21 = 2121
Step 102: 2121 + 21 = 2142
Step 103: 2142 + 21 = 2163
Step 104: 2163 + 21 = 2184
Step 105: 2184 + 21 = 2205
Step 106: 2205 + 21 = 2226
Step 107: 2226 + 21 = 2247
Step 108: 2247 + 21 = 2268
Step 109: 2268 + 21 = 2289
Step 110: 2289 + 21 = 2310
Step 111: 2310 + 21 = 2331
Step 112: 2331 + 21 = 2352
Step 113: 2352 + 21 = 2373
Step 114: 2373 + 21 = 2394
Step 115: 2394 + 21 = 2415
Step 116: 2415 + 21 = 2436
Step 117: 2436 + 21 = 2457
Step 118: 2457 + 21 = 2478
Step 119: 2478 + 21 = 2499
Step 120: 2499 + 21 = 2520
Step 121: 2520 + 21 = 2541
Step 122: 2541 + 21 = 2562
Step 123: 2562 + 21 = 2583
Step 124: 2583 + 21 = 2604
Step 125: 2604 + 21 = 2625
Step 126: 2625 + 21 = 2646
Step 127: 2646 + 21 = 2667
Step 128: 2667 + 21 = 2688
Step 129: 2688 + 21 = 2709
Step 130: 2709 + 21 = 2730
Step 131: 2730 + 21 = 2751
Step 132: 2751 + 21 = 2772
Step 133: 2772 + 21 = 2793
Step 134: 2793 + 21 = 2814
Step 135: 2814 + 21 = 2835
Step 136: 2835 + 21 = 2856
Step 137: 2856 + 21 = 2877
Step 138: 2877 + 21 = 2898
Step 139: 2898 + 21 = 2919
Step 140: 2919 + 21 = 2940
Step 141: 2940 + 21 = 2961
Step 142: 2961 + 21 = 2982
Step 143: 2982 + 21 = 3003
Step 144: 3003 + 21 = 3024
Step 145: 3024 + 21 = 3045
Step 146: 3045 + 21 = 3066
Step 147: 3066 + 21 = 3087
Step 148: 3087 + 21 = 3108
Step 149: 3108 + 21 = 3129
Step 150: 3129 + 21 = 3150
Step 151: 3150 + 21 = 3171
Step 152: 3171 + 21 = 3192
Step 153: 3192 + 21 = 3213
Step 154: 3213 + 21 = 3234
Step 155: 3234 + 21 = 3255
Step 156: 3255 + 21 = 3276
Step 157: 3276 + 21 = 3297
Step 158: 3297 + 21 = 3318
Step 159: 3318 + 21 = 3339
Step 160: 3339 + 21 = 3360
Step 161: 3360 + 21 = 3381
Step 162: 3381 + 21 = 3402
Step 163: 3402 + 21 = 3423
Step 164: 3423 + 21 = 3444
Step 165: 3444 + 21 = 3465
Step 166: 3465 + 21 = 3486
Step 167: 3486 + 21 = 3507
Step 168: 3507 + 21 = 3528
Step 169: 3528 + 21 = 3549
Step 170: 3549 + 21 = 3570
Step 171: 3570 + 21 = 3591
Step 172: 3591 + 21 = 3612
Step 173: 3612 + 21 = 3633
Step 174: 3633 + 21 = 3654
Step 175: 3654 + 21 = 3675
Step 176: 3675 + 21 = 3696
Step 177: 3696 + 21 = 3717
Step 178: 3717 + 21 = 3738
Step 179: 3738 + 21 = 3759
Step 180: 3759 + 21 = 3780
Step 181: 3780 + 21 = 3801
Step 182: 3801 + 21 = 3822
Step 183: 3822 + 21 = 3843
Step 184: 3843 + 21 = 3864
Step 185: 3864 + 21 = 3885
Step 186: 3885 + 21 = 3906
Step 187: 3906 + 21 = 3927
Step 188: 3927 + 21 = 3948
Step 189: 3948 + 21 = 3969
Step 190: 3969 + 21 = 3990
Step 191: 3990 + 21 = 4011
Step 192: 4011 + 21 = 4032
Step 193: 4032 + 21 = 4053
Step 194: 4053 + 21 = 4074
Step 195: 4074 + 21 = 4095
Step 196: 4095 + 21 = 4116
Step 197: 4116 + 21 = 4137
Step 198: 4137 + 21 = 4158
Step 199: 4158 + 21 = 4179
Step 200: 4179 + 21 = 4200
Step 201: 4200 + 21 = 4221
Step 202: 4221 + 21 = 4242
Step 203: 4242 + 21 = 4263
Step 204: 4263 + 21 = 4284
Step 205: 4284 + 21 = 4305
Step 206: 4305 + 21 = 4326
Step 207: 4326 + 21 = 4347
Step 208: 4347 + 21 = 4368
Step 209: 4368 + 21 = 4389
Step 210: 4389 + 21 = 4410
Step 211: 4410 + 21 = 4431
Step 212: 4431 + 21 = 4452
Step 213: 4452 + 21 = 4473
Step 214: 4473 + 21 = 4494
Step 215: 4494 + 21 = 4515
Step 216: 4515 + 21 = 4536
Step 217: 4536 + 21 = 4557
Step 218: 4557 + 21 = 4578
Step 219: 4578 + 21 = 4599
Step 220: 4599 + 21 = 4620
Step 221: 4620 + 21 = 4641
Step 222: 4641 + 21 = 4662
Step 223: 4662 + 21 = 4683
Step 224: 4683 + 21 = 4704
Step 225: 4704 + 21 = 4725
Step 226: 4725 + 21 = 4746
Step 227: 4746 + 21 = 4767
Step 228: 4767 + 21 = 4788
Step 229: 4788 + 21 = 4809
Step 230: 4809 + 21 = 4830
Step 231: 4830 + 21 = 4851
Step 232: 4851 + 21 = 4872
Step 233: 4872 + 21 = 4893
Step 234: 4893 + 21 = 4914
Step 235: 4914 + 21 = 4935
Step 236: 4935 + 21 = 4956
Step 237: 4956 + 21 = 4977
Step 238: 4977 + 21 = 4998
Step 239: 4998 + 21 = 5019
Step 240: 5019 + 21 = 5040
Step 241: 5040 + 21 = 5061
Step 242: 5061 + 21 = 5082
Step 243: 5082 + 21 = 5103
Step 244: 5103 + 21 = 5124
Step 245: 5124 + 21 = 5145
Step 246: 5145 + 21 = 5166
Step 247: 5166 + 21 = 5187
Step 248: 5187 + 21 = 5208
Step 249: 5208 + 21 = 5229
Step 250: 5229 + 21 = 5250
Step 251: 5250 + 21 = 5271
Step 252: 5271 + 21 = 5292
Step 253: 5292 + 21 = 5313
Step 254: 5313 + 21 = 5334
Step 255: 5334 + 21 = 5355
Step 256: 5355 + 21 = 5376
Step 257: 5376 + 21 = 5397
Step 258: 5397 + 21 = 5418
Step 259: 5418 + 21 = 5439
Step 260: 5439 + 21 = 5460
Step 261: 5460 + 21 = 5481
Step 262: 5481 + 21 = 5502
Step 263: 5502 + 21 = 5523
Step 264: 5523 + 21 = 5544
Step 265: 5544 + 21 = 5565
Step 266: 5565 + 21 = 5586
Step 267: 5586 + 21 = 5607
Step 268: 5607 + 21 = 5628
Step 269: 5628 + 21 = 5649
Step 270: 5649 + 21 = 5670
Step 271: 5670 + 21 = 5691
Step 272: 5691 + 21 = 5712
Step 273: 5712 + 21 = 5733
Step 274: 5733 + 21 = 5754
Step 275: 5754 + 21 = 5775
Step 276: 5775 + 21 = 5796
Step 277: 5796 + 21 = 5817
Step 278: 5817 + 21 = 5838
Step 279: 5838 + 21 = 5859
Step 280: 5859 + 21 = 5880
Step 281: 5880 + 21 = 5901
Step 282: 5901 + 21 = 5922
Step 283: 5922 + 21 = 5943
Step 284: 5943 + 21 = 5964
Step 285: 5964 + 21 = 5985
Step 286: 5985 + 21 = 6006
Step 287: 6006 + 21 = 6027
Step 288: 6027 + 21 = 6048
Step 289: 6048 + 21 = 6069
Step 290: 6069 + 21 = 6090
Step 291: 6090 + 21 = 6111
Step 292: 6111 + 21 = 6132
Step 293: 6132 + 21 = 6153
Step 294: 6153 + 21 = 6174
Step 295: 6174 + 21 = 6195
Step 296: 6195 + 21 = 6216
Step 297: 6216 + 21 = 6237
Step 298: 6237 + 21 = 6258
Step 299: 6258 + 21 = 6279
Step 300: 6279 + 21 = 6300
Step 301: 6300 + 21 = 6321
Step 302: 6321 + 21 = 6342
Step 303: 6342 + 21 = 6363
Step 304: 6363 + 21 = 6384
Step 305: 6384 + 21 = 6405
Step 306: 6405 + 21 = 6426
Step 307: 6426 + 21 = 6447
Step 308: 6447 + 21 = 6468
Step 309: 6468 + 21 = 6489
Step 310: 6489 + 21 = 6510
Step 311: 6510 + 21 = 6531
Step 312: 6531 + 21 = 6552
Step 313: 6552 + 21 = 6573
Step 314: 6573 + 21 = 6594
Step 315: 6594 + 21 = 6615
Step 316: 6615 + 21 = 6636
Step 317: 6636 + 21 = 6657
Step 318: 6657 + 21 = 6678
Step 319: 6678 + 21 = 6699
Step 320: 6699 + 21 = 6720
Step 321: 6720 + 21 = 6741
Step 322: 6741 + 21 = 6762
Step 323: 6762 + 21 = 6783
Step 324: 6783 + 21 = 6804
Step 325: 6804 + 21 = 6825
Step 326: 6825 + 21 = 6846
Step 327: 6846 + 21 = 6867
Step 328: 6867 + 21 = 6888
Step 329: 6888 + 21 = 6909
Step 330: 6909 + 21 = 6930
Step 331: 6930 + 21 = 6951
Step 332: 6951 + 21 = 6972
Step 333: 6972 + 21 = 6993
Step 334: 6993 + 21 = 7014
Step 335: 7014 + 21 = 7035
Step 336: 7035 + 21 = 7056
Step 337: 7056 + 21 = 7077
Step 338: 7077 + 21 = 7098
Step 339: 7098 + 21 = 7119
Step 340: 7119 + 21 = 7140
Step 341: 7140 + 21 = 7161
Step 342: 7161 + 21 = 7182
Step 343: 7182 + 21 = 7203
Step 344: 7203 + 21 = 7224
Step 345: 7224 + 21 = 7245
Step 346: 7245 + 21 = 7266
Step 347: 7266 + 21 = 7287
Step 348: 7287 + 21 = 7308
Step 349: 7308 + 21 = 7329
Step 350: 7329 + 21 = 7350
Step 351: 7350 + 21 = 7371
Step 352: 7371 + 21 = 7392
Step 353: 7392 + 21 = 7413
Step 354: 7413 + 21 = 7434
Step 355: 7434 + 21 = 7455
Step 356: 7455 + 21 = 7476
Step 357: 7476 + 21 = 7497
Step 358: 7497 + 21 = 7518
Step 359: 7518 + 21 = 7539
Step 360: 7539 + 21 = 7560
Step 361: 7560 + 21 = 7581
Step 362: 7581 + 21 = 7602
Step 363: 7602 + 21 = 7623
Step 364: 7623 + 21 = 7644
Step 365: 7644 + 21 = 7665
Step 366: 7665 + 21 = 7686
Step 367: 7686 + 21 = 7707
Step 368: 7707 + 21 = 7728
Step 369: 7728 + 21 = 7749
Step 370: 7749 + 21 = 7770
Step 371: 7770 + 21 = 7791
Step 372: 7791 + 21 = 7812
Step 373: 7812 + 21 = 7833
Step 374: 7833 + 21 = 7854
Step 375: 7854 + 21 = 7875
Step 376: 7875 + 21 = 7896
Step 377: 7896 + 21 = 7917
Step 378: 7917 + 21 = 7938
Step 379: 7938 + 21 = 7959
Step 380: 7959 + 21 = 7980

So, 21*380 = 7980